George Kontogeorgos

Classification and pathology of pituitary tumors.

Pituitary adenomas originating in adenohypophysial cells represent the most common neoplasms of the sella turcica. The pathologist’s goal is the optimal diagnosis and classification of pituitary adenomas. Lack of clinicopathological correlations in the past classification of pituitary adenomas, which was based on the tinctorial properties of adenoma cells, limited the importance of histological diagnosis. Morphologic separation of pituitary cells by electron microscopy provided fundamental knowledge to classify pituitary adenomas. Immunohistochemistry represents the gold standard of the current classification. Combined morphologic and immunohistochemical diagnostic approaches resulted in the clinicopathologic classification of pituitary adenomas. The WHO classification of 2004 is based on morphologic features and takes into consideration findings from imaging procedures and clinical symptoms. Morphologic characterization of pituitary tumors and correlation of the hormone product with hormone secretion provides the clinician with useful information. In addition, the utility of tumor markers offers objective information in managing the patient and predicting responses to specific treatment. The Ki-67 labeling index (LI) is widely used for it correlates with invasiveness and probably prognosis. Adenomas showing increased (>3%) LI and extensive p53 immunoreactivity should be termed “atypical adenomas” suggesting aggressive potential or malignant transformation. Morphologic separation of adenoma from carcinoma is not feasible. The term pituitary carcinoma should be exclusively applied when cerebrospinal and/or systemic metastases are definite.

Collision sellar lesions: experience with eight cases and review of the literature.

The concomitant presence of a pituitary adenoma with a second sellar lesion in patients operated upon for pituitary adenoma is an uncommon entity. Although rare, quite a great variety of lesions have been indentified coexisting with pituitary adenomas. In fact, most combinations have been described before, but an overview with information on the frequency of combined pathologies in a large series has not been published. We present a series of eight collision sellar lesions indentified among 548 transsphenoidally resected pituitary adenomas in two Neurosurgical Departments. The histological studies confirmed a case of sarcoidosis within a non-functioning pituitary adenoma, a case of intrasellar schwannoma coexisting with growth hormone (GH) secreting adenoma, two Rathke’s cleft cysts combined with pituitary adenomas, three gangliocytomas associated with GH-secreting adenomas, and a case of a double pituitary adenoma. The pertinent literature is discussed with emphasis on pathogenetic theories of dual sellar lesions. Although there is no direct evidence to confirm the pathogenetic relationship of collision sellar lesions, the number of cases presented in literature makes the theory of an incidental occurrence rather doubtful. Suggested hypotheses about a common embryonic origin or a potential interaction between pituitary adenomas and the immune system are presented.

Differential distribution of the neuron-associated class III β-tubulin in neuroendocrine lung tumors

OBJECTIVE To study the immunoreactivity profile of the neuron-associated class III beta-tubulin isotype (beta III) in epithelial lung tumors. DESIGN One hundred four formalin-fixed, paraffin-embedded primary and metastatic lung cancer specimens were immunostained with an anti-beta III mouse monoclonal antibody (TuJ1) and an anti-beta III affinity-purified rabbit antiserum. Paraffin sections from fetal, infantile, and adult nonneoplastic lung tissues were also examined. RESULTS In the fetal airway epithelium, beta III staining is detected transiently in rare Kulchitsky-like cells from lung tissues corresponding to the pseudoglandular and canalicular but not the saccular or alveolar stages of development. beta III is absent in healthy, hyperplastic, metaplastic, and dysplastic airway epithelium of the adult lung. In contrast, beta III is highly expressed in small cell lung cancer, large cell neuroendocrine carcinoma, and in some non-small cell lung cancers, particularly adenocarcinomas. There is no correlation between expression of beta III and generic neuroendocrine markers, such as chromogranin A and/or synaptophysin, in pulmonary adenocarcinomas. Also, focal beta III staining is present in primary and metastatic adenocarcinomas (to the lung) originating in the colon, prostate, and ovary. beta III is expressed to a much lesser extent in atypical carcinoids and is rarely detectable in typical carcinoids and squamous cell carcinomas of the lung. The distribution of beta III in small cell lung cancer and adenocarcinoma metastases to regional lymph nodes and brain approaches 100% of tumor cells, which is substantially greater than in the primary tumors. CONCLUSIONS In the context of neuroendocrine lung tumors, beta III immunoreactivity is a molecular signature of high-grade malignant neoplasms (small cell lung cancer and large cell neuroendocrine carcinoma) although its importance in atypical carcinoids must be evaluated further. In addition, beta III may be a useful diagnostic marker in distinguishing between small cell lung cancers and certain non-small cell lung cancers (poorly differentiated squamous cell carcinomas), especially in small biopsy specimens. To our knowledge, beta III is the only tumor biomarker that exhibits a substantially more widespread distribution in poorly differentiated than in better differentiated pulmonary neuroendocrine tumors. However, the significance of beta III phenotypes in non-small cell lung cancer, particularly adenocarcinoma, with respect to neuroendocrine differentiation and prognostic value, requires further evaluation.

Ganglion cell containing pituitary adenomas: signs of neuronal differentiation in adenoma cells

Ganglion cell containing pituitary adenomas are rare. They represent tumors originating in the sella turcica which are composed of adenomatous and neuronal components. Recently accumulated information suggests a common origin for their neuronal and pituitary constituents. The objective of this study was to report the clinical and morphologic findings of pituitary gangliocytomas and study their immunoprofile using neuronal markers. Seven cases of pituitary gangliocytomas retrieved from 1,322 sellar lesions were studied. All tumors were removed from patients with mild acromegaly. Histologically they were biphasic composed of pituitary adenoma and clusters of ganglion cells embedded in a variably dense neuropil substrate. All adenomas belonged to the category of sparsely granulated somatotroph adenoma and were positive for growth hormone, whereas in five tumors, a few adenoma cells were also positive for prolactin. Ganglion cells were immunoreactive for NSE, synaptophysin and neurofilament protein (NFP). NFP-reactive fibrils were observed in the neuropil substrate and varied in number among the cases. Interestingly, all tumors contained varying numbers of adenoma cells with NFP-positive, dot-like areas of cytoplasmic reactivity, mostly tiny paranuclear, a finding not previously reported in human pituitary gangliocytomas. The presence of NFP in pituitary adenomas indicates neuronal differentiation in adenoma cells, suggesting a common origin for neuronal and pituitary adenoma cell elements in gangliocytomas.

Interleukin-6, a growth promoting cytokine, is present in human pituitary adenomas: an immunocytochemical study.

OBJECTIVE The aim of this study was to investigate the presence of interleukin‐6 (IL‐6) in human pituitary adenomas.

Effect of Dopamine Agonists on Lactotroph Adenomas of the Human Pituitary.

Dopamine (DA) agonists cause reduction of blood prolactin level and tumor shrinkage in most patients with lactotroph adenoma. Our aim was to investigate the cellular mechanism of tumor shrinkage by determining mitotic, MIB-1, p27, and apoptotic indices, as well as microvessel density (MVD), surface microvessel density (SMD), ploidy, and other nuclear parameters. Surgically removed lactotroph adenomas were selected from 29 patients, of whom 19 were treated with oral bromocriptine (BEC), long-acting injectable BEC (BEC-LAR), or quinagolide and 10 were untreated. In treated adenomas mitotic and MIB-1 indices were lower, whereas the apoptotic indices were not significantly higher compared to untreated adenomas. The decrease in MIB-1 labeling reached significance in adenomas exposed to quinagolide (p<0.05). Aside from the BEC-LAR treated group, wherein p27 expression was significantly reduced (p<0.05), p27 expression did not differ significantly between the treated and untreated groups. MVD density was significantly lower in the treated adenomas, whereas the decrease in SMD did not attain significance. The DNA ploidy and most other nuclear parameters did not differ significantly in the two groups. In conclusion, reduction of mitotic and MIB-1 indices indicates that suppression of cell proliferation contributes to tumor shrinkage, whereas p27 protein expression and apoptosis play no major role in the adenoma involution. Further studies are required to explain the effect of DA agonists on MVD and SMD.

Localization of Epidermal Growth Factor (EGF) and Epidermal Growth Factor Receptor (EGFr) in Human Pituitary Adenomas and Nontumorous Pituitaries: An Immunocytochemical Study.

Epidermal growth factor (EGF) and epidermal growth factor receptor (EGFr) were investigated by immunocytochemistry (ICH) in 57 human pituitary adenomas and 10 nontumorous autopsy pituitaries. EGF immunoreactivity was demonstrated in 24 adenomas (42%), representing 23 functioning tumors and 1 nonfunctioning tumor of oncocytic type, and in all nontumorous pituitaries. Among 40 tumors, EGFr was found positive in 15 functioning adenomas (37.5%), representing 50% of them. The presence of both EGF and EGFr was found mainly in corticotroph adenomas (60%) and less frequently in somatotroph and lactotroph adenomas (20%). ICH on serial sections with EGF or EGFr and adrenocorticotrophic hormone (ACTH) or S-100 protein revealed that EGF and EGFr are localized specifically in corticotrophs and EGFr in stellate cells of nontumorous adenohypophysis.These results confirm the presence of EGF and EGFr in human pituitary adenomas and nontumorous pituitaries and highlight their frequent occurrence in hormone-producing adenomas. Further work is required to explore the possibility that EGF and EGFr play a role in hormone production, release, and tumor progression.

EZH2 is regulated by ERK/AKT and targets integrin alpha2 gene to control Epithelial-Mesenchymal Transition and anoikis in colon cancer cells.

Epithelial-Mesenchymal Transition is a good example of cell plasticity. In tumorigenesis, this process has been associated with metastasis. Overexpression of EZH2 has been detected in most malignant human tumors, including colorectal carcinomas. Herein, we provide evidence supporting the idea that oncogenic Epithelial-Mesenchymal Transition in colon cancer cell models is partially controlled by epigenetic factors such as the transcription regulator EZH2. Evaluation of EZH2 mRNA and protein levels revealed overexpression in cell lines with metastatic traits. Analysis of EZH2 mRNA expression was expanded in clinical samples of colon cancer, and high level of EZH2 correlates with appearance of metastasis. Furthermore, inhibition of ERK and AKT pathways in metastatic colon cancer cell lines attenuates EZH2 overexpression. EZH2 promoter analysis illustrates presence of putative AP-1 binding sites and occupancy of transcription factors such as FRA-1 and C-JUN is demonstrated here on EZH2 promoter. Abrogation of EZH2 expression impairs the ability of colon cancer cells to move associated with anoikis in three-dimensional environment. Integrin alpha2 was identified to be a novel EZH2 target by chromatin immunoprecipitation and short hairpin RNA analysis. This study proposes that activation of ERK/AKT pathways and FRA1/C-JUN induce EZH2 overexpression, which results in Integrin alpha2 silencing. Our results show how deregulation of epigenetic factors and mechanisms can affect cancer cell aggressiveness and propose EZH2 as a potential metastasis marker and/or therapeutic target for colorectal cancer treatment.

Null cell adenomas, oncocytomas, and gonadotroph adenomas of the human pituitary: An immunocytochemical and ultrastructural anafysis of 300 cases

The immunocytochemical profile of 300 clinically nonsecreting pituitary adenomas was investigated. All tumors were diagnosed, classified, and separated into null cell adenomas, oncocytomas, and gonadotroph adenomas according to their ultrastructural morphology. The immunocytochemical analysis was based on the semiquantitative proportional estimates of positive cells immunostained for all known peptide and glycoprotein pituitary hormones including alpha-subunit. The majority of tumors (87%) were to some extent immunopositive for various hormones. Glycoprotein hormones were most frequently encountered. Usually, particularly in males, more than one subunit was present in the same tumor. In 97 tumors (32%) more than 25% of adenoma cells were immunoreactive for gfycoprotein hormones. Fifty-five tumors (18%) contained occasional cells immunopositive for growth hormone (GH), prolactin (PRL), and adenocorticotropin (ACTH) in addition to glycoprotein hormones. Given the significant proportion of immunoreactive cells for gonadotropins and alpha-subunit, in tumors characterizedas null cell adenomas and oncocytomas, imrnunocytochemistry may provide valuable information to the pathologist and clinical endocrinologist contributing to the evaluation of this heterogeneous group of tumors.

Correlation of bcl-2 and bax with apoptosis in human pituitary adenomas.

Bcl-2 oncogene and Bax gene play an important role in regulating apoptosis. In the present study, the expression of bcl-2 and bax was investigated and correlated with apoptosis in a series of 81 pituitary adenomas. Bcl-2 and bax proteins were localized by immunohistochemistry and the histoscore (HSC) was assessed by multiplying the immunohistostaining grade (1 to 4) by the staining intensity grade (1 to 3). According to bcl-2/bax HSC the tumors were separated in group A when ≥1 and group B when <1. The apoptotic labeling index (ALI) was accessed by the in situ end-labeling (ISEL) technique. Bcl-2 protein was equally detected in functioning and nonfunctioning adenomas with statistically significant higher HSC in nonfunctioning tumors (P < 0.03). Bax protein was immunopositive in the substantial majority of adenomas with significantly higher HSC in functioning as compared to nonfunctioning adenomas (P < 0.0009). The ALI was significantly higher in functioning adenomas as compared to nonfunctioning adenomas (P < 0.04). In addition, ALI was significantly higher in group B than in group A (P < 0.004) and it was correlated with bax HSC (P < 0.004). Finally, the group B of bcl-2/bax significantly predominated in nonfunctioning tumors (P < 0.0009) and in microadenomas (P = 0.05), as compared with functioning adenomas and macroadenomas respectively. In conclusion, our findings suggest that bcl-2 and bax molecules play a role in the regulation of apoptotic mechanisms in pituitary adenomas.